compare side length ratio clear solution for Similar Triangles by yoichi - python coding challenges

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compare side length ratio solution in Clear category for Similar Triangles by yoichi

from itertools import combinations
from math import sqrt
from typing import List, Tuple
Coords = List[Tuple[int, int]]


def get_distance(coords):
    return sqrt(sum((coords[0][i]-coords[1][i])**2 for i in range(2)))


def get_sides_ratio(vertices):
    sides = sorted(map(get_distance, combinations(vertices, 2)))
    return (sides[1]/sides[0], sides[2]/sides[0])


def similar_triangles(coords_1: Coords, coords_2: Coords) -> bool:
    return get_sides_ratio(coords_1) == get_sides_ratio(coords_2)

Feb. 15, 2020

Comments:

Pouf on June 28, 2020, 8:03 p.m.
You can simplify get_distance with `math.hypot()`. Also, it works here but be careful when comparing floats with `==`, especially after a division, it is not reliable. You can use `round()`, `math.isclose()` or `statistics.stdev`...

vlad.bezden on Aug. 19, 2020, 1:16 a.m.
I like how you used combinations. Great job!

lrnx on Dec. 27, 2020, 9:33 p.m.
You don't actually need to bother with the square and the square root in the euclidian distance, a simple manhattan distance will do the job just fine :) <pre class='brush: python'>def get_distance(coords): sum(abs(i - j) for i, j in zip(*coords))) </pre>

ainoneko on July 30, 2021, 4:46 p.m.
I'm afraid rotations would break the manhattan distance. Try this, for example: `assert similar_triangles([(0, 0), (1, 0), (1, 1)], [(0, 0), (1, 1), (2, 0)]) is True, '45-degrees'`

yoichi on July 31, 2021, 2:04 a.m.
That's right. It is interesting. ``` getsidesratio(coords1):(1.0, 1.4142135623730951) getsidesratio(coords2):(1.0, 1.414213562373095) ``` Do we have to think about rounding?

ainoneko on Aug. 3, 2021, 1:36 p.m.
<blockquote> Do we have to think about rounding? </blockquote> We should think of it (or to check if the difference is small) when using floating-point numbers. But we don't have to if we manage to use only integers ^_^

Adrian_Goh on Jan. 7, 2021, 5:32 p.m.
Is there a reason why you didn't use from math import dist?

yoichi on Jan. 13, 2021, 10:45 a.m.
There is no particular reason. I didn't know math.dist.

CDG.Axel on Sept. 2, 2021, 9:28 a.m.
very short! bit sqrt is not necessary, cause you divide side lengths

sMiTeOne on March 24, 2022, 8:42 a.m.
Unexpected use of the combinations library. I didn't think of this before!

Nocturne13 on Dec. 29, 2023, 10:51 a.m.
Nice and compact functional programming solution. Nicely done.

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